The invention relates to a method of interconnecting a first and a second element by means of laser welding, the first element consisting at least partly of glass or ceramics, and the second element consisting at least partly of metal, the bond between both elements being formed by the glass or ceramic part of the first element and the metal part of the second element. Such a method may be used, for example, in the manufacture of optical equipment, vacuum tubes and picture tubes.
A method of the type described opening paragraph is known from GB No. 1228451. In that specification a description is given of a method in which a glass element or glass elements is or are laser welded to a metal element, both elements are heated to a temperature just below the softening temperature of the glass. By means of a laser beam which is focussed on the metal element at the location of the bond to be made the temperatures of the metal element and, through this element, of the glass element are raised at the location of the laser spot. This causes the glass to soften after which the bond is formed. By way of example, GB No. 1228451 describes the securing of an electrode grid in a picture tube. A disadvantage of this method is that both elements have to be heated to a high temperature and that the method has to be carried out in a furnace. One or both of the elements, or a part or parts of one or both elements, for example optical or electronic components, may become damaged by these high temperatures. During cooling of the bond differences formed in the coefficients of thermal expansion may lead to thermal stresses which may have detrimental effects. The relative positions of accurately bonded elements may change in the cooling process due to these differences in the coefficients of thermal expansion. After the elements have cooled, these positions may change with time owing to stresses present in both elements, which stresses are caused by differences in the coefficients of thermal expansion. Since the glass softens at the location of the bond during the laser welding process, it is difficult to form a bond having a high dimensional accuracy.